An international row is brewing between the Spanish Government and an American sea salvage company over what could be the most valuable shipwreck ever.

The salvage firm Sub Sea Research believes it has found what remains of the 64-cannon French ship, Notre Dame de Deliverance, which sank in a fierce storm 60 kilometres (40 miles) off Florida's Key West in 1755.

It was one of the richest ships ever lost

Greg Brooks Sub Sea Research co-owner

The merchant vessel was chartered by Spain to carry treasures extracted from mines in Mexico, Peru and Colombia.

Its cargo of gold bullion, gems, coins and silver is worth an estimated $3bn.

Legal fight

Now Sub Sea Research has to answer the claims to the wreck by Spain and France.

The Spanish position refers to the terms of a 1902 treaty with the US based on the fact that the shipwreck could contain the remains of the Spanish soldiers.

250 sunken Spanish galleons hold billions in treasure

The claim is also likely to note that the cargo belonged to the Spanish Government.

"They've cast a blanket over this thing before anybody really knows that it is the Deliverance," Guy Burnette, the salvage company's lawyer said.

"We think it is. We have good reason to believe it is."

Sunken treasure

The Sub Sea Research has produced an incomplete inventory of what was believed to be on board of the Notre Dame de Deliverance when it left the Cuban port of Havana.

The cargo included:

437 kilogram of gold bullion in 17 chests,

more than 15,000 gold coins

153 golden snuff boxes

six chests of gems

more than 1,000,000 silver pieces

14 kg of sliver ore

six pairs of diamond earrings

a diamond ring

"It was one of the richest ships ever lost," one of the owners of the company, Greg Brooks, told the Miami Daily Business Review.

The Deliverance's glimmering cargo is approximately 10 times larger than that found in 2000 on the galleon Nuestra Senora de Atocha, from which about $400m in treasure was retrieved.

Further claims

A Florida district judge has granted the Sub Sea Research permission to make its claim to the shipwreck.

But the US State Department said the company needed Spain's permission to recover the treasure.

The claim to the Deliverance is further complicated by the fact that the ship belonged to the French West Indies company.

Its crew was French and the wreck could be claimed as France's property.

Sub Sea Research claims that the French company is long defunct and there is no legal owner.

The company's divers say the 50.5-metre-long wooden ship has split into two parts, and the wreck is thought to be spread over 20-square-kilometre (eight-sq-mile) area.

About 250 Spanish ships which sunk in the 17th and 18th centuries are thought to have taken with them treasure worth billions of dollars.